Search

Our objective was to evaluate the use of Saccharomyces cerevisiae-derived yeast fraction and multispecie Bacillusproducts alone or in combination on health and performance during a 56-d feedlot receiving period.

This study evaluated the effects of Sweet Bran (SB) and wet distillers grains with solubles (WDGS) in the diet alone or in combination on performance and carcass characteristics of finishing beef cattle.

Liver abscesses (LAs) are a common and important problem in cattle because of their association with decreased growth and production, low carcass quality, and the significant economic losses associated with liver condemnation. Fusobacterium necrophorumhas traditionally been considered the primary etiologic agent of LA formation in cattle, but recent evidence has demonstrated that LA microbial communities are far more polymicrobial than previously believed. Here, we characterize microbial communities within multiple LAs from the same animal, provide evidence that some LAs may be seeded from the hindgut, identify biomarkers throughout the gut-liver axis that predict the presence of LAs, and demonstrate the impact of tylosin on microbial communities in the rumen, ileum, and colon. 16S rRNA gene sequencing was used to characterize communities from LA purulent material, as well as from the luminal and epithelia, communities in three gut locations (rumen, ileum, colon) within the same animals. A combination of QIIME2 and phyloseq were used to analyze sequence data, and microbial community composition was compared based on generalized UniFrac distances. Taxa discriminant of LA occurrence were identified using linear discriminant analysis effect size (LEfSe). Despite being the most abundant genus when averaged across all LA communities, Fusobacteriumspp. was not the predominant taxa in the majority of LAs. In fact, members of Bacteriodetes(largely Bacteroides, Porphyromonas) were the predominant taxa in more than one-half of all LA communities. Importantly, multiple LAs from the same animal had remarkably similar community structure, and multiple taxa including Bifidobacteriumspp., widely considered beneficial to gut barrier function in humans, were differentially abundant in both the foregut and hindgut between cattle that did and did not have LAs. Further, tylosin had little impact on the diversity and composition of microbial communities within LAs but did alter communities in the rumen and small intestine. In particular, members of the family Lachnospiraceaewere more abundant in the rumen and hindgut of animals given tylosin. Together, these results provide additional evidence challenging the traditional theory of LA etiology (that bacterial translocation occurs exclusively from the rumen) and provides evidence that barrier dysfunction in the gut may be the underlying cause of LA formation.

Sexed semen artificial insemination is a breeding technique that allows producers to shorten breeding seasons, optimize genetics through use of superior semen, create calves based on sex preference, and increase profitability. Sexed semen is a technology that sorts semen by differences in DNA content between X (female) and Y (male) bearing sperm. However, sexed semen practices have yet to be widely used in beef cows due to reduced sperm numbers, low conception rates, and increased costs. The objective of this study was to determine the effect of time of estrus upon fixed-time artificial insemination (FTAI) of sex-sorted semen on conception rate using two different estrous synchronization protocols. Multiparous commercial beef cows (n = 73) were randomized by age, body condition score (BCS), and days post-partum at the University of Arkansas Livestock and Forestry Research Station in Batesville. Both synchronization treatments (TRT) used a controlled internal drug releasing device (Eazi-breed CIDR; 1.38g progesterone) inserted intravaginally on d -14 of the protocol simultaneous to administration of prostaglandin F2α (PGF; 500µg cloprostenol sodium; Estrumate). In the first treatment (TRT 1; 7&7 Synch), gonadotropin-releasing hormone (GnRH; 86µg gonadorelin; Fertagyl) was administered on d -7. In the second treatment (TRT 2; 8&6 Synch), GnRH was administered on d -6. Both treatments were then administered PGF simultaneous to CIDR removal on d 0, 66 ± 2h before FTAI and administration of GnRH. Standing heat (estrus) was visually detected every 3 h for 30 min intervals between CIDR removal and FTAI. Heat detection patches were used in conjunction with visual detection of estrus. Time of estrus was signified as time of standing immobile when mounted in combination with presenting a patch score of 4 (>75% color removed). Time of estrus (TD) was deviated from time of FTAI and categorized into three equal time groups (Grp 1 = 0 to 11.0 h; Grp 2 = 11.01 to 22.0 h; and Grp 3 = 22.01 to 33.0 h). Conception rate (CR) was determined via ultrasound 37 ± 2 d after FTAI. Data were analyzed using the GLIMMIX procedure of SAS 9.4. CR did not differ by age of dam (P= 0.58), BCS (P= 0.48), or TRT (P= 0.83). However, TD had an effect on CR (P= 0.002); and resulted in CR of 45% (Grp 1), 87% (Grp 2), and 42% (Grp 3). In conclusion, these results indicate artificially inseminating cows with sexed semen between 11.01 and 22.0 h after time of standing estrus will increase pregnancy rates for multiparous commercial beef cattle.

Our objective was to evaluate subsequent feedlot performance and carcass characteristics of steers that previously grazed endophyte-infected fescue and received either a mineral only (MIN) supplement or a cumulative management (CM) strategy.

Our objective was to compare metaphylaxis with tulathromycin (META) and vaccination with a pentavalent modified-live virus respiratory vaccine (MLV) in high-risk feedlot calves and their influence on health and growth performance during a 56-d receiving period.

Vaccination is the act of administering a vaccine, whereas immunization may occur if appropriate time is allowed for a competent host immune system to respond to the antigen contained in a vaccine. Timing is critical to ensure bovine respiratory disease (BRD) vaccine safety, efficacy, and efficiency. The current review provides temporal considerations of BRD vaccination within the North American beef production system with focus on vaccination timing in high-risk, newly received beef stocker and feedlot cattle.

Auction-derived steers (n = 36; initial BW = 284 ± 11 kg) were received to compare performance, rumination characteristics, and rumen pH differences due to alternative ration energy densities and feed management strategies during a 56 d receiving study. Cattle were weighed on day -1 and randomized to 1 of 3 treatments. Time spent ruminating was quantified with a three-axis accelerometer ear-tag. Rumen pH and temperature were logged in a random subset (n = 6 per treatment) by a ruminal bolus. Cattle were processed identically and housed in individual pens. The modified-live virus respiratory vaccination was delayed until day 28. The finisher (FIN) cattle were provided their daily feed as a high energy density (1.39 Mcal NEg/kg) diet. The finisher + hay (FIN+H) cattle were provided the same diet but were also offered 0.5% BW DM as coastal Bermudagrass hay on days 1, 4, 7, 10, 13, 16, 19, 22, 25, and 28. The control (CON) cattle were fed a low energy density (0.93 Mcal NEg/kg) diet from day 0 to 7, then transitioned to the FIN diet by replacing an additional 25% of the daily feed call with FIN every 7 d until 100% of the diet was FIN on day 29. Feed offering for CON was increased more aggressively (0.45 kg DM daily for days 1 to 7, every other day for day 8 to 14) than FIN and FIN+H (0.45 kg DM every other day for days 1 to 7, daily for days 8 to 14). Performance and DMI were analyzed using PROC MIXED in SAS with treatment as a fixed effect. Rumination, pH, and temperature models included repeated measures. There was no treatment difference observed for BW, average daily gain (ADG), or G:F (P ≥ 0.12). There was a treatment × day interaction (P = 0.06) for rumen temperature, where FIN increased more rapidly following vaccination on day 28 compared to CON (P ≤ 0.04). Daily rumination minutes were greater (P < 0.01) for CON than FIN from days 7 to 22. Additionally, CON had the greatest (P < 0.01) hourly rumination from 2000 to 0800 hours. Lower minimum daily rumen pH occurred in FIN+H (P ≤ 0.06) on weeks 1, 2 and 6 to 8 compared to CON. There were minimal statistical differences in area under the curve or time below pH thresholds, probably due to large animal-to-animal variation. Hourly rumen pH was reduced (P ≤ 0.05) for FIN vs. FIN+H and CON during the initial 28 d, but greater (P = 0.05) for FIN and FIN+H during the final 28 d. When cattle are individually fed, greater energy density rations can be fed initially without compromising performance, but this needs to be evaluated in group pens where greater DMI variation is probable.

Vaccination is a critical component of cattle health management. Effective cattle vaccine programs should consider the timing of vaccination in relation to expected disease challenge, risk for wild-type exposure of various bovine pathogens, and host factors during vaccination. Nearly all consulting veterinarians recommend vaccination of stressed, high-risk calves on feedlot arrival. However, this recommendation fails to consider several factors associated with vaccine efficiency. Further research evaluating vaccine interactions in stressed cattle and potential additive effects of endotoxin from multiple bacterin administration may reveal new evidence-based vaccination guidelines for cattle in the various segments of beef and dairy production systems.

This study evaluated starch dilution with different sources of fiber from terminal implant to harvest on feedlot cattle performance, rumen buffering characteristics, and carcass outcomes. Steers (n = 416) were allocated to 48 pens in a randomized complete block design and assigned to 1 of 4 dietary treatments. Treatments were steam-flaked corn-based diets: CON; 7.5% corn stalks fed for the entire feeding period or CON followed by CS; 14.8% corn stalks, WD; 9.5% wet distillers grains with solubles and 7.5% corn stalks, or NR; 19.0% wet distillers grains with solubles and 0.0% corn stalks fed from terminal implant to harvest. Steers were transitioned to CS, WD, and NR over 6 d using a two-ration system. Within each pen, 2 steers received an indwelling rumen pH bolus and a 3-axis accelerometer ear-tag to quantify rumination. Treatment differences were considered statistically significant when P < 0.10. Dry matter (DM) and metabolizable energy (ME) intake were greatest for cattle consuming CS, intermediate for WD and CON, and least for NR (P <0.01). The average daily gain (ADG) did not differ among treatments (P= 0.18); however, feed efficiency (G:F) was least for NR, intermediate for WD, and greatest for CS and CON (P= 0.10). Steers consuming CS had more (P= 0.08) 12thrib fat than NR, WD, or CON, but no other differences (P≥ 0.24) in carcass characteristics were observed. A treatment × day interaction (P <0.01) was observed for daily rumination time and ruminal pH. Results suggest that increasing the concentration of corn stalks in the diet post-terminal implant increased DM and ME intake and rumination; replacing corn stalks with wet distillers grains with solubles improved G:F and reduced rumination with minimal impacts on ruminal pH.

Transition of newly received feedlot cattle from a forage- to grain-based diet is challenging, and the appropriate roughage level in receiving diets is debatable. Nutritionists must consider the paradox of dietary transition and roughage level to mitigate ruminal acidosis, yet concomitantly low feed intake presents difficulty in achieving nutrient requirements when metabolic demand is increased due to inherent stress and disease challenge during the receiving period. Previous research suggests that performance is improved at the expense of increased morbidity for newly received cattle consuming diets with less roughage and greater starch concentration. The clinical signs of bovine respiratory disease (BRD) and acute acidosis are analogous; therefore, it is probable that acidotic cattle are incorrectly diagnosed with BRD in both research and production settings. Additional research efforts have attempted to elucidate alterations in microbial populations and digestion, physiological response to inflammatory challenge, and immunological response to infectious bovine rhinotracheitis virus challenge in cattle consuming diets of various roughage levels. Furthermore, our understanding of the rumen microbiome is improving rapidly with culture-independent assays, products such as direct-fed microbials are available, and increased availability and use of fibrous byproduct ingredients requires further attention. Beef cattle nutritionists and producers should consider that the health benefit of receiving diets containing greater levels of roughage and lower energy may not compensate for the reduction in performance compared with feeding receiving diets with lower roughage and greater energy.

The study objectives were to determine the effect of oral hydration therapy and bovine respiratory disease (BRD) on rumination behavior, rumen pH, and rumen temperature. A random subset of high-risk, auction-sourced bulls from 3 truckload blocks (initial BW = 188.9 ± 19.1 kg) were fitted with a collar containing a 3-axis accelerometer to quantify rumination time and activity (n = 58) and administered a rumen pH and temperature data logging bolus (n = 33). At arrival, subset calves (n = 2 per pen) were balanced across treatment pens (n = 15 per treatment; n = 10 animals per pen) and randomized to receive 0.57 L water/45.4 kg BW from a modified oral drenching apparatus (H2O) or no water administration (CON). Standard arrival processing procedures were implemented including surgical castration. Modified-live virus respiratory vaccination was delayed until day 28. Technicians assigned a clinical illness score (CIS) daily; calves with CIS ≥ 2 and rectal temperature ≥ 40 °C were considered a BRD case (RCASE) and treated with an antimicrobial. The fixed effect of BRD cases vs. nontreated cohorts (RCON) was determined retrospectively using data from the accelerometer collar (n = 19 and 29) and rumen bolus (n = 12 and 21, for RCASE and RCON, respectively). Daily means and hourly means across days throughout the 56-d observation period were generated. Fixed effects were analyzed using the mixed model procedure with repeated measures. Daily rumen temperature was altered (P = 0.04) such that peak rumen temperature occurred earlier for H2O, whereas CON had increased (P ≤ 0.01) rumen temperature following delayed vaccination on day 28. Calves diagnosed with BRD had a transiently decreased (P = 0.04) active minutes between days 9 and 32, decreased (P < 0.01) active minutes between 0800 and 2000 h, decreased (P < 0.01) rumination time between 2000 and 0400 h, greater (P < 0.01) rumen temperature until delayed vaccination on day 28, and greater (P < 0.01) hourly rumen temperature between 0900 and 0300, and altered (P < 0.01) rumen pH. Earlier peak rumen temperature observed in H2O may indicate physiological modification enabling a more pronounced inflammatory response. Differences in rumination behavior and activity may be useful for early BRD detection.

Objectives of this experiment were to examine the effects of live yeast (LY) supplementation on immunological, physiological, and behavioral responses in steers experimentally challenged with Mannheimia haemolytica (MH). Thirty-six crossbred Angus steers (BW = 352 ± 23 kg) seronegative for MH were allocated within a 2 × 2 factorial arrangement: Factor 1 = roughage-based diet with LY (Saccharomyces cerevisiae boulardii CNCM I-1079, 25 g·per steer daily) or negative control (CON). Factor 2 = bronchoselective endoscopic inoculation with MH or phosphate buffer solution (PBS). Steers were fed their respective diets for 28 d prior to MH challenge on day 0. Reticulo-rumen temperature (RUT; ThermoBolus, Medria) was measured continuously at 5-min intervals and rectal temperature on days -4, 0, 1, 2, 3, 5, 7, 10, and 14 relative to MH inoculation. Compared with PBS-treated steers, the steers inoculated with MH had increased (P < 0.05) RUT from 2 to 24 h, reaching a zenith (>41 °C) 9 to 11 h post-MH challenge, whereas rectal temperature was increased (P < 0.04) in MH-inoculated steers on day 1 post-MH challenge. Supplementation with LY increased (P < 0.05) rectal temperature on days 0, 7, and 10, relative to CON steers. There were inoculation x day interactions (P < 0.01) for lymphocyte, neutrophil, leukocyte, and haptoglobin concentrations. Steers challenged with MH had increased (P < 0.05) neutrophil concentration from days 1 to 3, leukocyte concentration on days 1 and 2 and haptoglobin concentration on days 1 to 5 post-MH challenge compared with PBS-treated steers. Steers supplemented with LY exhibited increased (P < 0.02) cortisol throughout the study compared with the CON treatment. Following inoculation, MH-challenged steers exhibited reduced (P < 0.05) DMI, eating rate, frequency, and duration of bunk visit (BV) events compared with PBS-treated steers. Results from this study demonstrate that the experimental challenge model effectively stimulated acute-immune responses and behavioral changes that are synonymous with naturally occurring bovine respiratory disease (BRD). However, supplementation with LY minimally altered the impact of the MH challenge on physiological and behavioral responses in this study. Continuously measured RUT was more sensitive at detecting febrile responses to MH challenge than rectal temperature. These results serve to guide future research on behavioral and physiological alterations exhibited during a BRD infection.

The objective of this study was to evaluate a combination of best management practices strategy for steer calves grazing tall fescue pastures with a range of toxicity. The experiment was conducted over 2 grazing seasons (fall 2015 for 91 d and spring 2016 for 84 d). Steers (n= 80 within season, body weight [BW] = 197.0 ± 15.43 kg [fall] and 116.9 ± 4.88 [spring]) were stocked at 2.45 and 4.1 calves/ha in fall and spring, respectively, to 16 pastures with varying levels of toxicity based on interim ergovaline (EV) concentration within season. Pastures were assigned to either mineral (MIN, n= 8) only management (MGMT) or a cumulative MGMT (CM, n= 8). The CM treatment included an implant containing 40-mg trenbolone acetate, 8-mg estradiol, and 29-mg tylosin tartrate (Component TE-G with Tylan, Elanco Animal Health, Greenfield, IN), 150 mg/calf daily monensin (Elanco Animal Health), and 1% BW of a 50:50 corn gluten feed:soybean hull supplement (as-is basis). Data were analyzed within season using pasture as the experimental unit. For fall and spring, the EV concentration was 1,476 ± 883.2 and 1,173 ± 620.6 ppb, respectively, and ranged from 90 to 2,180 ppb. During the fall, forage allowance did not differ (P= 0.76) between CM and MIN. In the spring, however, forage allowance only differed for the month of June (P≤ 0.05, 2.55 vs. 3.22 ± 0.177 kg DM/kg BW, for MIN and CM, respectively). In the fall, average daily gain (ADG) responded to the simple effects of EV (P= 0.01) and MGMT (P< 0.001), and ADG for MIN steers was explained by ADG = 0.41 − 0.000064 × EV, whereas ADG for CM was explained by ADG = 1.05 − 0.000064 × EV. In the spring, there was an EV × MGMT interaction (P= 0.03) for ADG. For MIN, ADG = 0.80 − 0.000278 × EV, whereas for CM, ADG = 0.94 + 0.000001835 × EV. In spring, the ADG response to CM relative to MIN increased as EV increased. The CM strategy resulted in lower blood urea nitrogen than MIN in fall and spring (P< 0.01), but prolactin and serum Cu were not affected by MGMT in either season. In conclusion, performance was improved within the fescue belt by implementing feeding strategies using implants, ionophores, and supplementation, but a detailed economic analysis is warranted. Further research is needed to evaluate CM programs under varied stocking rates and in combination with dilution of endophyte-infected fescue pastures with nontoxic grasses or legumes.

Crossbred beef bulls (n= 180) were blocked by initial BW (337 ± 10.9 kg; six blocks) and assigned randomly to one of three treatments on day 0: 1) INJ; received 1 mL (100 mg Zn) of a Zn solution in each testis, 2) BAN; received blood- restrictive rubber band placed around the dorsal aspect of the scrotum, 3) BUL; bulls with testicles remaining intact in a randomized complete block design (three treatment pens per block and 10 cattle per pen). A subset of 54 animals (n= 3 per pen) was fitted with accelerometers on day 0 to quantify behavior variables continuously for 28 d. Testis width and scrotal circumference, and serum haptoglobin (days 0, 1, 3, 5, 7, and 14) and testosterone concentrations (every 28 d until slaughter) were also determined for the subset. During the slaughter process, testes from INJ and BUL were collected to assess final testes weight and for histopathological evaluation. Data were analyzed using a mixed model (α = 0.05); pen served as the experimental unit for all dependent variables. Final BW was greater (P< 0.01) for INJ and BUL compared to BAN (672, 686, and 611 kg, respectively; SEM = 4.4). Overall ADG and G:F were greater (P≤ 0.03) in INJ and BUL than BAN; whereas, DMI was similar between treatments for the study duration (P= 0.46). Histopathological evaluation (n= 13; INJ = 7; BUL = 6) indicated that INJ testes were degenerative and reproductively nonviable whereas BUL testes were normal. Serum testosterone concentrations on day 168 were similar (P= 0.14) between INJ and BUL whereas after day 14, BAN was nondetectable; however, initial serum testosterone concentrations were similarly low across treatments. Serum haptoglobin concentration was greater (P< 0.01) in INJ than BUL and BAN on days 1, 3, 5, and 7. Scrotal circumference (P= 0.08) and testis width (P= 0.07) on day 168 tended to be greater for BUL than INJ. Motion index (P≤ 0.02) and step count (P= 0.04) was greater in BUL and INJ compared to BAN cattle during the 28 d monitoring period. No difference in standing time (P≥ 0.85) or lying bouts (P= 0.35) occurred. Zinc injection resulted in sterilization but did not cause complete cessation of testicular function evidenced by testosterone concentrations more similar to BUL than BAN. This resulted in overall increased BW and G:F for INJ vs. BAN, yet the acute phase response was markedly greater directly after Zn injection. Collectively, Zn injection resulted in outcomes more similar to BUL than BAN, implying minimal efficacy of INJ as a castration method in older bulls arriving to the feedlot.

Experimental bovine respiratory syncytial virus (BRSV) infection can enhance Histophilus somni(Hs) disease in calves; we thus hypothesized that modified-live virus (MLV) vaccines containing BRSV may alter Hscarriage. Our objective was to determine the effects of an intranasal (IN) trivalent (infectious bovine rhinotracheitis virus [IBRV], parainfluenza-3 virus [PI3V], and BRSV) respiratory vaccine with parenteral (PT) bivalent bovine viral diarrhea virus (BVDV) type I + II vaccine, or a PT pentavalent (BVDV type I and II, IBRV, BRSV, and PI3V) respiratory vaccine, on health, growth, immunity, and nasal pathogen colonization in high-risk beef calves. Calves (n= 525) were received in five truckload blocks and stratified by body weight (213 ± 18.4 kg), sex, and presence of a pre-existing ear-tag. Pens were spatially arranged in sets of three within a block and randomly assigned to treatment with an empty pen between treatment groups consisting of: 1) no MLV respiratory vaccination (CON), 2) IN trivalent MLV respiratory vaccine with PT BVDV type I + II vaccine (INT), or 3) PT pentavalent, MLV respiratory vaccine (INJ). The pen was the experimental unit, with 15 pens/treatment and 11 to 12 calves/pen in this 70-d receiving study. Health, performance, and BRSV, Hs, Mycoplasma bovis(Mb), Mannheimia haemolytica(Mh), and Pasteurella multocida(Pm) level in nasal swabs via rtPCR was determined on days 0, 7, 14, and 28, and BRSV-specific serum neutralizing antibody titer, and serum IFN-γ concentration via ELISA, were evaluated on days 0, 14, 28, 42, 56, and 70. Morbidity (P= 0.83), mortality (P= 0.68) and average daily gain (P≥ 0.82) did not differ. Serum antibodies against BRSV increased with time (P< 0.01). There was a treatment × time interaction (P< 0.01) for Hsdetection; on days 14 and 28, INT (21.1% and 57.1%) were more frequently (P< 0.01) Hspositive than CON (3.6% and 25.3%) or INJ (3.4 % and 8.4%). Also, INT had reduced (P= 0.03) cycle time of Hspositive samples on day 28. No difference (P≥ 0.17) was found for IFN-γ concentration and Mb, Mh,or Pmdetection. The proportion of Mhpositive culture from lung specimens differed (P< 0.01); INT had fewer (0.0%; 0 of 9) Mhpositive lungs than INJ (45.5%; 6 of 13) or CON (74.0%; 14 of 19). Vaccination of high-risk calves with MLV did not clearly impact health or growth during the receiving period. However, INT was associated with an altered upper respiratory microbial community in cattle resulting in increased detection and level of Hs.Intranasal MLV vaccination was associated with increased carriage of Histophilus somniin the naris, providing evidence that intranasal but not parenteral MLV vaccination can be associated with alterations in the carriage of this bacterial pathogen in the upper respiratory tract of cattle. Further research is needed to better understand how intranasal MLV vaccination impacts the respiratory microbiota and the clinical significance of such impact.Our objective was to determine the safety, efficiency, and effects on immunity and nasal shedding of respiratory pathogens for high-risk cattle administered an intranasal (IN), trivalent (infectious bovine rhinotracheitis virus [IBRV], parainfluenza-3 virus [PI3V], and bovine respiratory syncytial virus [BRSV]) respiratory vaccine with parenteral, bivalent bovine viral diarrhea virus (BVDV), or a parenteral, pentavalent (BVDV type I and II, IBRV, BRSV, and PI3V) respiratory vaccine, compared to an unvaccinated negative control. The results of this study indicate that modified-live virus (MLV) vaccination of high-risk calves upon arrival, either parenterally or intranasally, did not clearly impact health or growth during the feedlot receiving period. However, cattle that were intranasally vaccinated had increased carriage of Histophilus somniin the naris, greater amount of H. somniin nasal swabs indicated by reduced PCR cycle time, and less frequent culture of Mannheimia haemolyticafrom lung tissue samples upon necropsy. Therefore, intranasal administration of MLV vaccines may alter the microbial community and balance of opportunistic pathogens in the respiratory tract of cattle.

Despite research and increased availability of antimicrobials, the prevalence and challenges associated with BRD in stocker and feedlot operations remain. Preconditioned calves can better handle the transition from the origin ranch to the feedlot, yet there is incentive for buyers to purchase high-risk cattle at a reduced cost, and this is influenced by the proven efficacy and availability of antimicrobial metaphylaxis. The poor sensitivity of current BRD field diagnostic methods, typical pathogenesis of BRD, and labor issues are additional reasons to use metaphylaxis. Nevertheless, practitioners should consider comprehensive and novel approaches to judiciously guide decisions on metaphylactic use of antimicrobials.

This study evaluated the impacts of feeding a high-energy finishing diet during both the receiving and finishing period compared with a lower-energy receiving diet with adaptation to the finishing diet on health, performance, serum chemistry, ruminal pH, rumination, and carcass characteristics of high-risk feedlot cattle. Five truck-load blocks of steers (n= 101) and bulls (n= 299) were used in a generalized complete block design and randomly assigned to receive: 1) finishing diet for the entire feeding period (FIN) or 2) receiving diet for the first 56 d, followed by a transition to the finishing diet (REC). All cattle were fed ad libitum and consumed the same diet by day 74. A subset of cattle (n= 48) was randomly selected to quantify ruminal pH, temperature, and rumination time. Ultrasound images were collected on days 0, 74, and 146 to determine fat thickness over the 12th rib and rump, and carcass characteristics were determined after slaughter. Cattle fed FIN had less (P< 0.01) dry matter intake (DMI) from days 0 to 74, but DMI did not differ (P= 0.80) after day 74. From days 0 to final, DMI was 0.26 kg less for FIN compared with REC (P= 0.01). However, calculated metabolizable energy intake was not different from days 0 to 74 (P= 0.19), days 74 to final (P= 0.80), or overall (P= 0.78). Body weight (BW) on day 74 was greater (P< 0.01) and final BW tended to be greater (P= 0.10) for FIN compared with REC. Cattle consuming FIN had greater (P< 0.01) average daily gain and increased (P< 0.01) gain:feed from days 0 to 74. There were no differences (P≥ 0.31) in health outcomes. On day 74, FIN had greater (P= 0.04) fat thickness over the rump and rib but did not differ (P≥ 0.52) on day 146. Carcasses of FIN had greater (P= 0.04) hot carcass weight with no difference (P≥ 0.11) in ribeye area, 12th rib fat thickness, yield grade, or quality grade. There was no difference (P= 0.18) in liver abscess rate. There was a diet × day interaction for blood urea nitrogen (P= 0.02) such that concentration decreased from days 0 to 28 in both treatments, but was less on day 28 for FIN. Ruminal pH was greater on days 2 and 61 and rumination time was less from days 0 to 28 for FIN (diet × day interaction; P< 0.01). Overall, these results suggest that providing a finishing diet fed ad libitum to high-risk calves upon arrival may be a viable alternative to a low-energy receiving diet.High-risk cattle may not require a low-energy receiving diet containing high proportions of roughage upon arrival to the feedlot.When high-risk cattle arrive at the feedlot, they have low feed consumption and a greater risk for disease because of stress, inflammation, and exposure to pathogens. Because of reduced feed consumption, newly arrived cattle may not be able to meet their energy requirement for growth during the first several weeks after feedlot arrival. Therefore, providing a high-energy finishing diet (FIN) when stressed cattle arrive at the feedlot may allow for greater growth performance and improved health when compared with a traditional, low-energy receiving diet that contains more roughage (REC). Our study evaluated this concept and we observed that cattle fed FIN had greater body weight, average daily gain, and gain:feed (G:F) within the first 56 d when the different diets were fed, with no difference in growth performance after the cattle consuming REC transitioned to FIN on day 74. However, cattle consuming FIN had greater hot carcass weight and G:F over the entire feeding period. There were no differences in health outcomes among treatments. Overall, providing a high-energy finishing diet to high-risk cattle upon arrival to the feedlot improved growth performance with no impact on health.